The patent document DE 623 128 discloses an electrical plug connector with a pin shaped plug and a sleeve shaped coupling which encloses the plug with an annular intermediary cavity in inserted condition, this means when the plug is inserted into the coupling. A stack of flat or disc shaped contact elements is arranged in the intermediary cavity which contact elements are made from electrically conductive material, in particular metal. In one embodiment the contact elements are washers stamped from sheet metal with an inner circular ring in their center and two circular arc shaped spring arms which enclose the circular ring at a radial distance. The first ends of the spring arms are free at the second ends the spring arms integrally transition into the inner circular ring. The spring arms contact the inside of the sleeve shaped coupling and load the inner circular ring in radial direction in a spring elastic manner, so that the circular ring is arranged in the coupling in an eccentrial manner. The contact elements that are arranged in the sleeve shaped coupling in a stacked manner are arranged rotated relative to one another by 180° in an alternating manner, so that their inner rings are arranged in an alternating opposite eccentrical manner in the coupling. The plug which has a slightly smaller diameter than the rings of the contact elements centers the inner rings of the contact elements so that the inner rings contact the plug in a spring elastic manner. This way the spring arms of the washer shaped contact elements of the known electrical plug connector generate a contact pressure at the sleeve shaped coupling and also at the pin shaped plug, wherein the contact pressure provides a reliable electrically conductive connection of the plug with the coupling through the contact elements.
In a second embodiment the contact elements of the known electrical plug connector are bent from wire material. They include an open inner ring, this means an inner ring that is interrupted at one location and which is bent at sides of the opening of the ring by 180° towards the outside to form circular arc shaped spring arms which enclose the interrupted inner ring at a radial distance on the outside.